Electrodeposition of tin-gold alloys



Patented Apr. 25, 1933' UNITED STATES PATENT OFFICE HAROLD J. KERSTEN, OF CIN CINNATL' OHIO, ASSIGNOB TO BOARD OF DIRECTORS OF THE UNIVERSITY OF CINCINNATI, OF CINCINNATI, OHIO ELECTRODEPOSITION OF TIN-GOLD ALLOYS No Drawing.

The object of my inventionis to produce deposits of white gold comprising primarily gold and tin, which deposits are suitable for use in the jewelry art and respond to the accepted jewelers test for go1d,-i. e. which are not attacked by concentrated and dilute nitric acid. I I

Another object of my'invention is the provision of an electrolytic bath and a treatment suitable for the control of such deposits. These and \other objects of my invention which will be set forth hereinafter or will be apparent to one skilled in the art upon reading these specifications, I accomplish by that certain procedure and in that article of which I shall now describe a preferred embodiment.

In the practice of my invention I employ an electrolyte comprising salts of gold and of tin. The bath may contain alkali cyanides of gold, together with alkali stannates, alkali 'stannites, saltstoincrease the conductivity, to produce bu-fi'er action, to alter the degree of dissociation of the gold and tin salts, and organic or inorganic compounds for the purpose of preventing de- EOIIIIIPOSItIOII of the other constituentsof the In particular, I have found the following bath to produce satisfactory deposits:

Gold potassium cyanide (KAu( ON 3 gm. Potassium stannate K SnO :3H O 10 gm. Water 1 liter The composition and color of the alloy deposited may be altered by changing the .current density, the size of the anode, and

the temperature of the bath, the hydrogen 'ion concentration of the bath, the proportions of the components and the amount of agitation given to the bath during the electrodeposition. By way of example I may Application filed February 20, 1930. Serial No..430,135.

as hereinabove indicated, the composition of mybath and the electric conditions under which it is used may be varied, all without departing from the scope of my invention.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. A homogeneous dense electro-deposit of white gold comprising tin and gold as its'major constituent, the said deposit being unattacked by nitric acid.

2. An electroplating bath for producing white gold comprisin a cyanide salt of gold and a tin salt o an alkali metal, in water solution, the relative proportion of gold to tin in said electrolyte being IOWI 3. An electrolytic bathfor depositing white gold comprising an alkali cyanide of 5. A process for producing white gold electro-deposits, comprising, employing an electrolyte containing a gold salt and a tin salt, the relative proportion of gold to'tin in the electrolyte being low, and plating I from said electrolyte with an insoluble anode and a current density around one ampere per square centimeter.

6. An electrolyte for producing white gold deposits having substantially the following proportions Gold potassium cyanide (KAu (ON) 3 gml Potassium stannate K SnO 3H Ol 10 gm.

Water 1 liter HAROLD- 3. KERS'Ii EN. 

